Enhanced adsorption of Congo red using chitin suspension after sonoenzymolysis

In the present work, chitin suspensions after enzymolysis and sonoenzymolysis were taken as adsorbents to evaluate the adsorption properties of Congo red (CR) dyes. Compared with untreated chitin suspension, the CR adsorption performance was significantly improved after enzymolysis and even more after sonoenzymolysis. According to different adsorption kinetic and isotherm models, Langmuir isotherm and the pseudo-second order model were more reliable to describe the adsorption process of CR onto different chitin samples and demonstrated a monolayer and favorable physisorption process. What's more, negative values of ΔG (Gibbs free energy change) and the shifts to higher negative values with the temperature increasing from adsorption thermodynamic study proved a spontaneous CR adsorption process. The structural characterization before and after adsorption further verified the physical adsorption between chitin and CR, and a larger specific area and higher porosity of chitin suspension was obtained after sonoenzymolysis with more available active sites.